SFTPGo

Full featured and highly configurable SFTP server

Features

• Each account is chrooted to his Home Dir.
• SFTP accounts are virtual accounts stored in a "data provider".
• SQLite, MySQL, PostgreSQL and bbolt (key/value store in pure Go) data providers are supported.
• Public key and password authentication. Multiple public keys per user are supported.
• Quota support: accounts can have individual quota expressed as max total size and/or max number of files.
• Bandwidth throttling is supported, with distinct settings for upload and download.
• Per user maximum concurrent sessions.
• Per user permissions: list directories content, upload, download, delete, rename, create directories, create symlinks can be enabled or disabled.
• Per user files/folders ownership: you can map all the users to the system account that runs SFTPGo (all platforms are supported) or you can run SFTPGo as root user and map each user or group of users to a different system account (*NIX only).
• Configurable custom commands and/or HTTP notifications on upload, download, delete or rename.
• Automatically terminating idle connections.
• Atomic uploads are configurable.
• Optional SCP support.
• REST API for users and quota management and real time reports for the active connections with possibility of forcibly closing a connection.
• Configuration is a your choice: JSON, TOML, YAML, HCL, envfile are supported.
• Log files are accurate and they are saved in the easily parsable JSON format.

Platforms

SFTPGo is developed and tested on Linux. After each commit the code is automatically built and tested on Linux and macOS using Travis CI. Regularly the test cases are manually executed and pass on Windows. Other UNIX variants such as *BSD should work too.

Requirements

• Go 1.12 or higher.
• A suitable SQL server or key/value store to use as data provider: PostreSQL 9.4+ or MySQL 5.6+ or SQLite 3.x or bbolt 1.3.x

Installation

Simple install the package to your $GOPATH with the go tool from shell:

$ go get -u github.com/drakkan/sftpgo

Make sure Git is installed on your machine and in your system's PATH.

SFTPGo depends on go-sqlite3 that is a CGO package and so it requires a C compiler at build time. On Linux and macOS a compiler is easy to install or already installed, on Windows you need to download MinGW-w64 and build SFTPGo from its command prompt.

The compiler is a build time only dependency, it is not not required at runtime.

If you don't need SQLite, you can also get/build SFTPGo setting the environment variable GCO_ENABLED to 0, this way SQLite support will be disabled but PostgreSQL, MySQL and bbolt will work and you don't need a C compiler for building.

Version info, such as git commit and build date, can be embedded setting the following string variables at build time:

• github.com/drakkan/sftpgo/utils.commit
• github.com/drakkan/sftpgo/utils.date

For example you can build using the following command:

go build -i -ldflags "-s -w -X github.com/drakkan/sftpgo/utils.commit=`git describe --always --dirty` -X github.com/drakkan/sftpgo/utils.date=`date -u +%FT%TZ`" -o sftpgo

and you will get a version that includes git commit and build date like this one:

sftpgo -v
SFTPGo version: 0.9.0-dev-90607d4-dirty-2019-08-08T19:28:36Z

For Linux, a systemd sample service can be found inside the source tree.

Alternately you can use distro packages:

• Arch Linux PKGBUILD is available on AUR

For macOS a launchd sample service can be found inside the source tree. The launchd plist assumes that sftpgo has /usr/local/opt/sftpgo as base directory.

Configuration

The sftpgo executable can be used this way:

Usage:
  sftpgo [command]

Available Commands:
  help        Help about any command
  serve       Start the SFTP Server

Flags:
  -h, --help      help for sftpgo
  -v, --version

The serve subcommand supports the following flags:

• --config-dir string. Location of the config dir. This directory should contain the sftpgo configuration file and is used as the base for files with a relative path (eg. the private keys for the SFTP server, the SQLite or bblot database if you use SQLite or bbolt as data provider). The default value is "." or the value of SFTPGO_CONFIG_DIR environment variable.
• --config-file string. Name of the configuration file. It must be the name of a file stored in config-dir not the absolute path to the configuration file. The specified file name must have no extension we automatically load JSON, YAML, TOML, HCL and Java properties. The default value is "sftpgo" (and therefore sftpgo.json, sftpgo.yaml and so on are searched) or the value of SFTPGO_CONFIG_FILE environment variable.
• --log-compress boolean. Determine if the rotated log files should be compressed using gzip. Default false or the value of SFTPGO_LOG_COMPRESS environment variable (1 or true, 0 or false). It is unused if log-file-path is empty.
• --log-file-path string. Location for the log file, default "sftpgo.log" or the value of SFTPGO_LOG_FILE_PATH environment variable. Leave empty to write logs to the standard error.
• --log-max-age int. Maximum number of days to retain old log files. Default 28 or the value of SFTPGO_LOG_MAX_AGE environment variable. It is unused if log-file-path is empty.
• --log-max-backups int. Maximum number of old log files to retain. Default 5 or the value of SFTPGO_LOG_MAX_BACKUPS environment variable. It is unused if log-file-path is empty.
• --log-max-size int. Maximum size in megabytes of the log file before it gets rotated. Default 10 or the value of SFTPGO_LOG_MAX_SIZE environment variable. It is unused if log-file-path is empty.
• --log-verbose boolean. Enable verbose logs. Default true or the value of SFTPGO_LOG_VERBOSE environment variable (1 or true, 0 or false).

If you don't configure any private host keys, the daemon will use id_rsa in the configuration directory. If that file doesn't exist, the daemon will attempt to autogenerate it (if the user that executes SFTPGo has write access to the config-dir). The server supports any private key format supported by crypto/ssh.

Before starting sftpgo a dataprovider must be configured.

Sample SQL scripts to create the required database structure can be found inside the source tree sql directory. The SQL scripts filename's is, by convention, the date as YYYYMMDD and the suffix .sql. You need to apply all the SQL scripts for your database ordered by name, for example 20190706.sql must be applied before 20190728.sql and so on.

The sftpgo configuration file contains the following sections:

• "sftpd", the configuration for the SFTP server
  • bind_port, integer. The port used for serving SFTP requests. Default: 2022
  • bind_address, string. Leave blank to listen on all available network interfaces. Default: ""
  • idle_timeout, integer. Time in minutes after which an idle client will be disconnected. 0 menas disabled. Default: 15
  • max_auth_tries integer. Maximum number of authentication attempts permitted per connection. If set to a negative number, the number of attempts are unlimited. If set to zero, the number of attempts are limited to 6.
  • umask, string. Umask for the new files and directories. This setting has no effect on Windows. Default: "0022"
  • banner, string. Identification string used by the server. Leave empty to use the default banner. Default "SFTPGo_version"
  • upload_mode integer. 0 means standard, the files are uploaded directly to the requested path. 1 means atomic: files are uploaded to a temporary path and renamed to the requested path when the client ends the upload. Atomic mode avoids problems such as a web server that serves partial files when the files are being uploaded. In atomic mode if there is an upload error the temporary file is deleted and so the requested upload path will not contain a partial file.
  • actions, struct. It contains the command to execute and/or the HTTP URL to notify and the trigger conditions
    • execute_on, list of strings. Valid values are download, upload, delete, rename. On folder deletion a delete notification will be sent for each deleted file. Actions will be not executed if an error is detected and so a partial file is uploaded or downloaded. Leave empty to disable actions.
    • command, string. Absolute path to the command to execute. Leave empty to disable. The command is invoked with the following arguments:
      • action, any valid execute_on string
      • username, user who did the action
      • path to the affected file. For rename action this is the old file name
      • target_path, non empty for rename action, this is the new file name
    • http_notification_url, a valid URL. An HTTP GET request will be executed to this URL. Leave empty to disable. The query string will contain the following parameters that have the same meaning of the command's arguments:
      • action
      • username
      • path
      • target_path, added for rename action only
  • keys, struct array. It contains the daemon's private keys. If empty or missing the daemon will search or try to generate id_rsa in the configuration directory.
    • private_key, path to the private key file. It can be a path relative to the config dir or an absolute one.
  • enable_scp, boolean. Default disabled. Set to true to enable SCP support. SCP is an experimental feature, we have our own SCP implementation since we can't rely on scp system command to proper handle permissions, quota and user's home dir restrictions. The SCP protocol is quite simple but there is no official docs about it, so we need more testing and feedbacks before enabling it by default. We may not handle some borderline cases or have sneaky bugs. Please do accurate tests yourself before enabling SCP and let us known if something does not work as expected for your use cases. SCP between two remote hosts is supported using the -3 scp option.
  • kex_algorithms, list of strings. Available KEX (Key Exchange) algorithms in preference order. Leave empty to use default values. The supported values can be found here: crypto/ssh
  • ciphers, list of strings. Allowed ciphers. Leave empty to use default values. The supported values can be found here: crypto/ssh
  • macs, list of strings. available MAC (message authentication code) algorithms in preference order. Leave empty to use default values. The supported values can be found here: crypto/ssh
  • login_banner_file, path to the login banner file. The contents of the specified file, if any, are sent to the remote user before authentication is allowed. It can be a path relative to the config dir or an absolute one. Leave empty to send no login banner
• "data_provider", the configuration for the data provider
  • driver, string. Supported drivers are sqlite, mysql, postgresql, bolt
  • name, string. Database name. For driver sqlite this can be the database name relative to the config dir or the absolute path to the SQLite database.
  • host, string. Database host. Leave empty for driver sqlite and bolt
  • port, integer. Database port. Leave empty for driver sqlite and bolt
  • username, string. Database user. Leave empty for driver sqlite and bolt
  • password, string. Database password. Leave empty for driver sqlite and bolt
  • sslmode, integer. Used for drivers mysql and postgresql. 0 disable SSL/TLS connections, 1 require ssl, 2 set ssl mode to verify-ca for driver postgresql and skip-verify for driver mysql, 3 set ssl mode to verify-full for driver postgresql and preferred for driver mysql
  • connectionstring, string. Provide a custom database connection string. If not empty this connection string will be used instead of build one using the previous parameters. Leave empty for driver bolt
  • users_table, string. Database table for SFTP users
  • manage_users, integer. Set to 0 to disable users management, 1 to enable
  • track_quota, integer. Set the preferred way to track users quota between the following choices:
    • 0, disable quota tracking. REST API to scan user dir and update quota will do nothing
    • 1, quota is updated each time a user upload or delete a file even if the user has no quota restrictions
    • 2, quota is updated each time a user upload or delete a file but only for users with quota restrictions. With this configuration the "quota scan" REST API can still be used to periodically update space usage for users without quota restrictions
• "httpd", the configuration for the HTTP server used to serve REST API
  • bind_port, integer. The port used for serving HTTP requests. Set to 0 to disable HTTP server. Default: 8080
  • bind_address, string. Leave blank to listen on all available network interfaces. Default: "127.0.0.1"

Here is a full example showing the default config in JSON format:

{
  "sftpd": {
    "bind_port": 2022,
    "bind_address": "",
    "idle_timeout": 15,
    "max_auth_tries": 0,
    "umask": "0022",
    "banner": "SFTPGo",
    "actions": {
      "execute_on": [],
      "command": "",
      "http_notification_url": ""
    },
    "keys": [],
    "enable_scp": false
  },
  "data_provider": {
    "driver": "sqlite",
    "name": "sftpgo.db",
    "host": "",
    "port": 5432,
    "username": "",
    "password": "",
    "sslmode": 0,
    "connection_string": "",
    "users_table": "users",
    "manage_users": 1,
    "track_quota": 2
  },
  "httpd": {
    "bind_port": 8080,
    "bind_address": "127.0.0.1"
  }
}

If you want to use a private key that use an algorithm different from RSA or more than one private key then replace the empty keys array with something like this:

"keys": [
  {
    "private_key": "id_rsa"
  },
  {
    "private_key": "id_ecdsa"
  }
]

The configuration can be read from JSON, TOML, YAML, HCL, envfile and Java properties config files, if your config-file flag is set to sftpgo (default value) you need to create a configuration file called sftpgo.json or sftpgo.yaml and so on inside config-dir.

You can also override all the available configuration options using environment variables, sftpgo will check for environment variables with a name matching the key uppercased and prefixed with the SFTPGO_. You need to use __ to traverse a struct.

Let's see some examples:

• To set sftpd bind_port you need to define the env var SFTPGO_SFTPD__BIND_PORT
• To set the execute_on actions you need to define the env var SFTPGO_SFTPD__ACTIONS__EXECUTE_ON for example SFTPGO_SFTPD__ACTIONS__EXECUTE_ON=upload,download

Please note that to override configuration options with environment variables a configuration file containing the options to override is required. You can, for example, deploy the default configuration file and then override the options you need to customize using environment variables.

To start the SFTP Server with the default values for the command line flags simply use:

sftpgo serve

Account's configuration properties

For each account the following properties can be configured:

• username
• password used for password authentication. For users created using SFTPGo REST API if the password has no known hashing algo prefix it will be stored using argon2id. SFTPGo supports checking passwords stored with bcrypt and pbkdf2 too. For pbkdf2 the supported format is $<algo>$<iterations>$<salt>$<hashed pwd base64 encoded>, where algo is pbkdf2-sha1 or pbkdf2-sha256 or pbkdf2-sha512. For example the pbkdf2-sha256 of the word password using 150000 iterations and E86a9YMX3zC7 as salt must be stored as $pbkdf2-sha256$150000$E86a9YMX3zC7$R5J62hsSq+pYw00hLLPKBbcGXmq7fj5+/M0IFoYtZbo=. For bcrypt the format must be the one supported by golang's crypto/bcrypt package, for example the password secret with cost 14 must be stored as $2a$14$ajq8Q7fbtFRQvXpdCq7Jcuy.Rx1h/L4J60Otx.gyNLbAYctGMJ9tK. Using the REST API you can send a password hashed as bcrypt or pbkdf2 and it will be stored as is.
• public_keys array of public keys. At least one public key or the password is mandatory.
• home_dir The user cannot upload or download files outside this directory. Must be an absolute path
• uid, gid. If sftpgo runs as root system user then the created files and directories will be assigned to this system uid/gid. Ignored on windows and if sftpgo runs as non root user: in this case files and directories for all SFTP users will be owned by the system user that runs sftpgo.
• max_sessions maximum concurrent sessions. 0 means unlimited
• quota_size maximum size allowed as bytes. 0 means unlimited
• quota_files maximum number of files allowed. 0 means unlimited
• permissions the following permissions are supported:
  • * all permission are granted
  • list list items is allowed
  • download download files is allowed
  • upload upload files is allowed
  • delete delete files or directories is allowed
  • rename rename files or directories is allowed
  • create_dirs create directories is allowed
  • create_symlinks create symbolic links is allowed
• upload_bandwidth maximum upload bandwidth as KB/s, 0 means unlimited
• download_bandwidth maximum download bandwidth as KB/s, 0 means unlimited

These properties are stored inside the data provider. If you want to use your existing accounts, you can create a database view. Since a view is read only, you have to disable user management and quota tracking so SFTPGo will never try to write to the view.

REST API

SFTPGo exposes REST API to manage users and quota and to get real time reports for the active connections with possibility of forcibly closing a connection.

If quota tracking is enabled in sftpgo configuration file, then the used size and number of files are updated each time a file is added/removed. If files are added/removed not using SFTP or if you change track_quota from 2 to 1, you can rescan the user home dir and update the used quota using the REST API.

REST API is designed to run on localhost or on a trusted network, if you need HTTPS or authentication you can setup a reverse proxy using an HTTP Server such as Apache or NGNIX.

For example you can keep SFTPGo listening on localhost and expose it externally configuring a reverse proxy using Apache HTTP Server this way:

ProxyPass /api/v1 http://127.0.0.1:8080/api/v1
ProxyPassReverse /api/v1 http://127.0.0.1:8080/api/v1

and you can add authentication with something like this:

<Location /api/v1>
	AuthType Digest
	AuthName "Private"
	AuthDigestDomain "/api/v1"
	AuthDigestProvider file
	AuthUserFile "/etc/httpd/conf/auth_digest"
	Require valid-user
</Location>

and, of course, you can configure the web server to use HTTPS.

The OpenAPI 3 schema for the exposed API can be found inside the source tree: openapi.yaml.

A sample CLI client for the REST API can be found inside the source tree scripts directory.

You can also generate your own REST client, in your preferred programming language or even bash scripts, using an OpenAPI generator such as swagger-codegen or OpenAPI Generator

Logs

Inside the log file each line is a JSON struct, each struct has a sender fields that identify the log type.

The logs can be divided into the following categories:

• "app logs", internal logs used to debug sftpgo:
  • sender string. This is generally the package name that emits the log
  • time string. Date/time with millisecond precision
  • level string
  • message string
• "transfer logs", SFTP/SCP transfer logs:
  • sender string. Upload or Download
  • time string. Date/time with millisecond precision
  • level string
  • elapsed_ms, int64. Elapsed time, as milliseconds, for the upload/download
  • size_bytes, int64. Size, as bytes, of the download/upload
  • username, string
  • file_path string
  • connection_id string. Unique connection identifier
  • protocol string. SFTP or SCP
• "command logs", SFTP/SCP command logs:
  • sender string. Rename, Rmdir, Mkdir, Symlink, Remove
  • level string
  • username, string
  • file_path string
  • target_path string
  • connection_id string. Unique connection identifier
  • protocol string. SFTP or SCP
• "http logs", REST API logs:
  • sender string. httpd
  • level string
  • remote_addr string. IP and port of the remote client
  • proto string, for example HTTP/1.1
  • method string. HTTP method (GET, POST, PUT, DELETE etc.)
  • user_agent string
  • uri string. Full uri
  • resp_status integer. HTTP response status code
  • resp_size integer. Size in bytes of the HTTP response
  • elapsed_ms int64. Elapsed time, as milliseconds, to complete the request
  • request_id string. Unique request identifier

Acknowledgements

• pkg/sftp
• go-chi
• zerolog
• lumberjack
• argon2id
• go-sqlite3
• go-sql-driver/mysql
• bbolt
• lib/pq
• viper
• cobra
• xid

Some code was initially taken from Pterodactyl sftp server

License

GNU GPLv3